1. Field of the Invention
The present invention relates to a photo sensor, a flat panel display device using the photo sensor and a process of fabricating a dark diode, and more particularly, to a photo sensor and a flat panel display device using the photo sensor outputting a signal responding to only light.
2. Description of the Related Art
Recently, various flat panel display (FPD) devices having reduced weight and volume, which are unfavorable in a cathode ray tube (CRT), have been developed. As flat panel display devices, there are liquid crystal display devices, field emission display devices, plasma display panels, organic light emitting display devices and other related display devices.
The organic light emitting display device displays an image using an organic light emitting diode (OLED) generating light by recombination of an electron and a hole.
The organic light emitting display device has various advantages such as an excellent color representation, a thin thickness, and other related advantages, so that the organic light emitting display device is widely used in a variety of applications such as PDAs (personal digital assistants), MP3 devices, and other related electronic devices, in addition to a cellular phone.
Visibility of the displayed image on such a flat panel display device may vary with the brightness of ambient light. In other words, even though an image is displayed with the same brightness, when the brightness of the ambient light is relatively high, the displayed image may appear darker to users' bare eyes, and when the brightness of the ambient light is relatively low, the displayed image may appear brighter to users' bare eyes.
Therefore, in order to enhance visibility of the displayed image to users' bare eyes, the brightness of the ambient light is sensed, wherein when the brightness of the ambient light is relatively high, the brightness of the displayed image may be raised, and when the brightness of the ambient light is relatively low, the brightness of the displayed image may be lowered. Also, when the brightness of an image is controlled according to the brightness of the ambient light, the brightness of the displayed image will not be unnecessarily raised, and thus possibly reducing the power consumption of the display device.
Based on the reasons mentioned above, there has been contrived a method to control the brightness of the displayed image corresponding to the ambient light by attaching a photo sensor sensing the ambient light to a flat panel display device.
The photo sensor includes a photodiode, which is sensitive to the temperature. Therefore, when the ambient temperature rises to a predetermined degree, an electrical current generated by temperature becomes significantly larger than an electrical current generated by light in the photodiode so that the electrical currents generated by light may be ignored. Therefore, in order to complement brightness corresponding to the ambient light for the display device, the electrical current generated from the photodiode should be compensated by temperature.